Discbrake to sprocket adapter

Ratking

Ratking

1 kW
Joined
May 20, 2010
Messages
494
Location
Norway
Hello

I was thinking about how to use a spragbearing/freebearing when this just jumped out of my head. Its easily made in aluminum and I just have to press the bearing to it.
This will replace the brakedisc at the rearwheel, and I really don't need so much brakepower at the rearwheel so v brake will do. Anyone tried this before?
I saw some bearings at http://www.vxb.com/page/bearings/PROD/One-Way-Bearings/Kit10973 and they are so much cheaper than a eno freewheel and maybe stronger. I would like to read the tecnichal sheet, but I havent found it jet.

Then I have to make a adapter from the bearing to the sprocket, and its good to go.


Hub.png


Hubogdrev.png
 
Hi Ratking,

http://www.stieber.de/pdf/stieber/CSK-product-en.pdf

Also, see page 11: http://www.stieber.de/download/STB_2010_07_en.pdf

I assume the VXB ones are Chinese...at that price.....?

Check there's enough room within the frame... :)

I used a CSK35 on my bike - on the RH side, though..
 
Hello

I have to check the frame for space before I make any of the parts, but do you think this is doable?
I would guess that the wheelhub will shatter before the bearing or any other part of the system.

The reasen why I want to get the sprocket on the left side is because of the gearbox. I found a cheap grinder rated to 2Kw with bearings and pretty nice gears.
I dont see anyone use a grinder gearbox, but at the same time, I dont see anyone that use a gearbox at all, only belts and chains.
 
Yes, I'm sure it's doable. It's on my list of things to do.....

You'll probably need a substantial offset on your bearing to sprocket adaptor, to position the sprocket closer to the spokes for frame clearance.
 
I machined an adapter for a fixed sprocket and had to put in an offset towards the inside of the wheel in order to for the 52 tooth sprocket to clear the chain stay. You will likely run into this same issue.

Here is a similar idea that might work. I saw where someone machined the disk brake mount down and put left hand threads on it to mount a south paw freewheel. The only problem with this is that I don’t think you can find a good quality south paw freewheel that will take a lot of power. I am using one on an electric assist bike and it works fine, but I don’t do full power starts. Instead of threads you could turn it down smooth and press the sprag clutch on.

Bubba
 
You definitely want to go with the German bearings, even if they are expensive. I have experience with both the Chinese and the German ones, and the Chinese ones have been known to fail (don't lock and run in both directions). I was a service tech for a product that used them. They had to do a recall and replace the Chinese bearings they tried to save money on, and put German ones back in because the Chinese ones failed. There is no where near the force on the bearings in the product I serviced than there would be in an ebike.

Clay
 
The German or Japanese ones are more expensive than an ENO freewheel, though :) I think my Japanese CSK35 was around £75..($110) and that was 3 years ago...
 
If you check out how a sprague clutch works, it's just friction of a smooth metal surface getting pushed against another smooth metal surface greased surface (not kidding). When they are properly designed, they do work decently well, but anything with a postive engaugement dog setup is going to be worlds stronger. The ENO's hold over 600ft-lbs of torque, and will continue to maintain that sort of torque ability as long as the dogs still fall into the slots (at very long time).

Sprague clutches get surface imperfections from shock loads, and pretty soon an oval roller ends up trying to load on an imperfection. The moment this happens, the loading of the center is no long symetrically balanced, so it can't function to evenly distribute loads between the other oval rollers, more surface imperfections are made from the ensueing slip, and torque handling ability decreases with each time this happens.

If you never have shock load exceed the safe load rating for them, then they can last and work well for a pretty long time. They can't match the robust nature of what a dog freewheel can handle though, but for low powered bikes I'm sure it would work fine. :)
 
Then theres only one problem, Im going for ether hxt 6Kw or the collosus 12Kw. So I guess the eno freewheel is the way to go.
Its really important that the powertrain withstands a bit of abuse, I want wheelies and fun. I guess the search for a decent freewheel aint over yet :(
 
Ratking said:
Then theres only one problem, Im going for ether hxt 6Kw or the collosus 12Kw.
Click to expand...
Ah, right... Why not have the freewheel further up the drivetrain, then? It doesn't sound like you'll be pedalling it without the motor, much... ENO don't do a LH freewheel, anyway (I guess you could have one broached and reverse mount it, though..). Or, you could try using a CSK40.
 
Just install the freewheel on the output shaft of your drive (or motor) like I do with my setups. That also makes the disc brake to sprocket adaptor much easier to make.

Matt
 
Hello Ratking,
I don't know how tight your budget is but here is a few looky looks at off the shelf components. The big issue with left side drive is the free wheeling (as you are finding out) and the tight frame spacing on that side of the bike.
here is a thread that keeps things on the left.
http://endless-sphere.com/forums/viewtopic.php?f=28&t=13862
this will limit the gearing choices for pedaling.
Unless your set up with some welding abilities to modify your rear spacing it will be a choice based on your priorites. (time,money,patiance)

If you have a "freehub" style rear, there is the broached freewheel option but that is kind of spendy for a 1st build.(if that is the case)
hope this helps, good luck. T
 
I wanted to try another route than a eno freewheel because I didn't believe it could hold the torque that the bigger motors produce, but 600ft lbs of torque is allot.
If that's the case I don't see any reason to try to invent the wheel ones more.

I think this drawing describes what I wanted to make, but if the spragbearings don't handle the torque there's now way I want to spend time and money try to get it to work.


Hubogdrev2.png
 
There is very little noticeable drag (not enough to even feel) with the left side chain always spinning. In fact, you really do not even notice any decrease is coasting distance. I have been running systems like this for two years without any issues what-so-ever.

Matt
 
recumpence said:
There is very little noticeable drag (not enough to even feel) with the left side chain always spinning. In fact, you really do not even notice any decrease is coasting distance. I have been running systems like this for two years without any issues what-so-ever.

Matt
Click to expand...

You also mention the 'slack' is less running fixed rear sprocket and freewheel on the motor side of things Matt.

KiM
 
Hello

Thanks for the input, I'm starting to get a good view on how to make the power train.

This is my plan so far( after some good advice from you);

Motor(hxt 6kw or collosus 12kw)->Grinder gearbox(3,75:1)->Eno 16t freewheel->56t sprocket(3,5:1)
This gives me; motor 7500 rpm at 100v->output gearbox 2000 rpm-> eno and rear sprocket gives 570 rpm at the wheel.

2 * pi * 33cm(26"/2)=207,24cm x 570=118126,8 cm/min

118126,8/60=1968,78 cm/t

1968,78/100=19,68 km/t

Is this correct?
I read in on post that the rearwheel should have around 500rpm to achieve good topspeed, but that dosent make any sense if my math is correct.
 
Seems like a reasonable plan :)

118126.8 cm/min. (x0.0006) = 70.9 km/h :wink:

[NB: If 75rpm/V is the velocity constant, the motor won't output any torque at 7500rpm.......Use something like 7500rpm * 0.9 = 6750 rpm]
 
Maybe it's clearer to say to convert cm/min to km/h you need to divide by 100,000: the number of cm in a kilometer. That gets you km/minute. Then you multiply by 60, the number of minutes in an hour. That gets you km/hr. Easy way, multiply by 0.00001 (km/cm) x 60 (min/hr) = 0.0006

Miles said:
Seems like a reasonable plan :)

118126.8 cm/min. (x0.0006) = 70.9 km/h :wink:

[NB: If 75rpm/V is the velocity constant, the motor won't output any torque at 7500rpm.......Use something like 7500rpm * 0.9 = 6750 rpm]
Click to expand...
 
Thankyou very much :D

I'd hoped for some clever minds to help me out. Thats perfect for my need.
I just hope that the motor wont be to stressed under hard acceleration.
Are there any experience with how much a normal bikechain can handle?
I would love to just use off-the-shelf parts thats easy to get hold of when they break.
 
Ratking,

You will likely need a chain tensioner with that layout.

If you weren't using the angle-grinder gearbox, you could have used the cranks as a jackshaft - seeing as they are concentric with the swing arm pivot.
 
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